There are known certain devices designed to detect the failure in any one of guide lamps simply by the occurence of a breakage of the circuit to which such numerous lamps are connected in series. Such known devices have a drawback in that failure of one lamp results in extinction of all of the remaining lamps.
Improvements have been made in which a switch is provided, as illustrated in FIG. 6 of the accompanying drawings, to give a short circuit to the terminals of each of serially connected lamps so that failure of any one lamp does not affect all the other lamps. However, this circuit device has the disadvantage that it is difficult to know which of so many remotely located lamps has failed and therefore to monitor all the lamps centrally from one place.
With the foregoing difficulties of the prior art in view, the present invention seeks to provide a device for detecting lamp failure which is capable of performing accurate detection and remote central monitoring of a large number of electric lamps.